In my opinion, scotchbrite became popular because it's main predecessor was sandpaper. On a spinner with water supply water can flow through the pad which made it easier to get a more uniform surface over the whole ball.
I also still use them occasionally, but typically the medium and finer grits rather than the maroon or green. Their cost is less than the newer abrasives that can be expensive comparatively.
Having said that, a green pad with compound on it can produce an aggressive surface that can still be very useful today. I compare it to Brunswick's older generation Rough Buff surface. Changing speeds, water flow, and hand pressure can get some nice results without much cost.